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41.
A multi-lithology diffusive stratigraphic model is considered, which simulates at large scales in space and time the infill
of sedimentary basins governed by the interaction between tectonics displacements, eustatic variations, sediment supply, and
sediment transport laws. The model accounts for the mass conservation of each sediment lithology resulting in a mixed parabolic,
hyperbolic system of partial differential equations (PDEs) for the lithology concentrations and the sediment thickness. It
also takes into account a limit on the rock alteration velocity modeled as a unilaterality constraint. To obtain a robust,
fast, and accurate simulation, fully and semi-implicit finite volume discre tization schemes are derived for which the existence
of stable solutions is proved. Then, the set of nonlinear equations is solved using a Newton algorithm adapted to the unilaterality
constraint, and preconditioning strategies are defined for the solution of the linear system at each Newton iteration. They
are based on an algebraic approximate decoupling of the sediment thickness and the concentration variables as well as on a
proper preconditioning of each variable. These algorithms are studied and compared in terms of robustness, scalability, and
efficiency on two real basin test cases. 相似文献
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岩质高边坡稳定性的分析评价涉及工程地质学、岩体力学、计算科学等多学科交汇的问题,是一较为复杂的系统工程问题。在系统分析岩质高边坡赋存的地质背景和环境条件的基础上,采用系统分析评价、综合集成的方法应是研究分析和解决该问题的有效和最佳方法。针对漳龙高速公路石崆山Ⅱ段岩质高边坡工程,在系统分析边坡工程地质特性的基础上,采用赤平极射投影法和有限单元(FEM)法等,进行综合评价和系统分析,获得的稳定性结论,已正常运营使用若干年,反映了系统分析,综合评价方法是成功和有效的。它表明,综合评价、系统分析应是岩质高边坡稳定性评价分析的重要途径;它的综合内容和集成方式及其完善与工程实用性,有待进一步深入的研究和工程实践的运用及其经验的积累。 相似文献
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A multi-method approach to study the stability of natural slopes and landslide susceptibility mapping 总被引:8,自引:0,他引:8
In this paper, a multi-method approach for the assessment of the stability of natural slopes and landslide hazard mapping applied to the Dakar coastal region is presented. This approach is based on the effective combination of geotechnical field and laboratory works, of GIS, and of mechanical (deterministic and numerical) stability analysis. By using this approach, valuable results were gained regarding instability factors, landslide kinematics, simulation of slope failure and coastal erosion. This led to a thorough assessment and strong reduction in the subjectivity of the slope stability and hazard assessment and to the development of an objective landslide danger map of the SW coast of Dakar. Analysis of the results shows that the slides were influenced by the geotechnical properties of the soil, the weathering, the hydrogeological situation, and the erosion by waves. The landslide susceptibility assessment based on this methodological approach has allowed for an appropriate and adequate consideration of the multiple factors affecting the stability and the optimization of planning and investment for land development in the city. 相似文献
47.
48.
Oxygen deficient perovskites in the system CaSiO3–CaAlO2.5 and implications for the Earth’s interior
U. W. Bläß F. Langenhorst D. J. Frost F. Seifert 《Physics and Chemistry of Minerals》2007,34(6):363-376
Oxygen deficient perovskites of the system CaSiO3–CaAlO2.5 have been synthesised at high-pressure and -temperature conditions relevant to the Earth’s transition zone in order to investigate
their stabilities in the Earth’s mantle and determine structural properties associated with vacancy incorporation. Two polysomes
of thermodynamically stable defect perovskites with Ca(Al0.4Si0.6)O2.8 and Ca(Al0.5Si0.5)O2.75 stoichiometry have been identified. The ordering of oxygen defects into pseudo-cubic (111) layers results in well-ordered
ten- or eightfold superstructures, respectively. At all other compositions examined, a metastable formation of perovskites
has been observed instead, which are assumed to grow initially disordered. These are now characterised by tiny domains, formed
due to subsequent ordering of vacancies along various pseudo-cubic {111} layers. Both ordered defect perovskites show a large
P–T stability field ranging from about 9–18 GPa and 4–12 GPa, respectively. Microstructural TEM analyses revealed the presence
of growth and ferroelastic twins, which indicate a phase transition from rhombohedral to monoclinic symmetry during quenching.
Electron energy loss spectroscopy of Si and Al K edges point at the presence of tetrahedral, octahedral and maybe some pentacoordinated silicon, whereas aluminium is predominantly
octahedrally coordinated with minor fractions in lower coordination. Observed properties are interpreted in terms of a new
structural model, explaining the observed phase transition and formation of different twin laws as well as giving reasons
for the development of such large superstructures. With respect to phase relations of the transition zone, the potential occurrence
of such defect perovskites in the Earth’s interior is discussed. 相似文献
49.
某边坡变形破坏机理的数值分析 总被引:3,自引:0,他引:3
某花岗岩矿岩土体主要有填土、粉质粘土、淤泥及淤泥质土、含泥中粗砂、粘土、残积砂质粘土,其下为花岗岩基岩。边坡最大高度75m,其中残积土层以上的土质边坡高度约50m。本文运用有限元强度折减法对该边坡的稳定性进行了研究,得出了潜在的破坏模式及各个滑动部分的安全系数。分析结果表明,本边坡存在3个潜在滑动面,其中两个为浅层滑动面,另一个为深层滑动面。两个浅层滑动面的稳定系数在1.13~1.17,处于临界状态。深层滑动面稳定性系数在1.29,目前尚处在相对稳定状态。根据分析结果,提出了如下加固措施:(1)对滑坡体进行削坡处理;(2)在其滑动面下方设置抗滑台阶;(3)采用预应力锚索框架梁结合肋柱进行加固处理。 相似文献
50.
Influence of earthquakes on the stability of slopes 总被引:2,自引:0,他引:2
Robert Hack Dinand Alkema Gerard A.M. Kruse Noud Leenders Lucia Luzi 《Engineering Geology》2007,91(1):4-15
Earthquakes are a major trigger for instability of natural and man-made slopes. Often the instability of slopes due to an earthquake causes more destruction and kills more people than the actual earthquake itself. A comparison is made between different methodologies to analyze the potential stability of slopes during earthquakes. Theoretically, it seems simple to calculate the stability of a slope during an earthquake. In reality, however, the stability is influenced by so many parameters that are either not known or which influence is so poorly known that a decent estimation of stability cannot be made. Offshore the situation is worse because proper data required for stability calculations are even less available than onshore. On- and offshore, erosion and weathering create continuously slopes that may become unstable during a future earthquake, offshore also sedimentation creates continuously new slopes. Another fundamental problem in stability analysis is the complicated and largely unknown behavior of seismic waves in three-dimensions in natural materials. The lack of accurate data and the unknown behavior of seismic waves in three-dimensions make estimations of slope stability during an earthquake unreliable. 相似文献